Most Don Rosa stories have the letters D.U.C.K. hidden somewhere in the first panel. Rosa's covers also usually have D.U.C.K. in them. This is an acronym for Dedicated to Unca Carl from Keno. Because Disney would not allow for personal signatures in the comics, and thought that D.U.C.K. looked too much like one, Don Rosa has made a habit of hiding the letters in various unlikely places. Many of his readers have made a sport out of finding them. D.U.C.K. is in most cases hidden in the very first image, on the first page of the story. D.U.C.K. is also often hidden in Rosa's cover-art, which he makes for his own stories and reprints of old Carl Barks stories.
— Wikipedia